Warsaw and other Polish cities, as well as Smolensk in Russia will hold ceremonies today to mark four years since the plane carrying President Lech Kaczynski and 95 other people including Poland’s top officials crashed in Smolensk, western Russia.

The delegation was en route to memorial ceremonies in Katyn for thousands of Polish army officers killed by the Soviet secret police in 1940.

Polish Prime Minister Donald Tusk will take part in an official service at the Powazki military cemetery in Warsaw while Polish President Bronislaw Komorowski and First lady will attend a service in the chapel of the Presidential Palace.

A recent poll by Millward Brown shows that 32% of Poles believe that the Smolensk plane crash was caused by pressure on pilots to land in poor weather conditions.

Some 30% of Poles believe that a mistake of the pilots or air controllers was the reason for the crash. 29% claim it was general chaos that led to the tragedy. 23% of the surveyed believe the deaths resulted from a coup.